Fontconfig error: No writable cache directories?

Just happened to notice that since mid april, on Arch x86_64, the following sort of messages in uwsgi@trytond:

uwsgi[2575]: Fontconfig error: No writable cache directories
uwsgi[2575]: Fontconfig error: No writable cache directories
uwsgi[2575]: convert /tmp/trytond_e0r42s7l/account.invoice.odt -> /tmp/trytond_e0r42s7l/account.invoice.pdf using filter : writer_pdf_Export

apparently any report invoking relatorio generates this, namely sales&invoices.

Any idea how to get it fixed right?

For info, under uwsgi, user&group are set to ‘tryton’ and under the home directory for ‘tryton’, all the files and directories under .config and .cache are owned by ‘tryton:tryton’…

At a loss as to what else could be at hand, other than /tmp…

Cheers